1. Field of the Invention
The present invention relates to a herbicide containing phytopathogenic microorganisms for surface application on water comprising phytopathogenic microorganisms which are pathogenic against non-useful plants having a hydrophobic surface, and are themselves hydrophobic on the surface but with virtually no adhered surfactant, and a submersible base, and a process for producing the same.
2. Description of the Related Art
Environmental pollution caused by excessive use of synthetic organic agricultural chemicals or reduced herbicidal effectiveness due to the appearance of pathogenic insects or weeds which have developed chemical resistance has become a serious social problem. The effects of synthetic organic agricultural chemicals on humans or the natural environment have become a media issue. Biological agricultural agents have attracted attention as a solution to these problems, and research and development in this field has been facilitated.
Research and development into herbicides containing phytopathogenic microorganisms has been active primarily in the United States. Today, DeVine (a product of Abbott Laboratories) using chlamydospores of Phytophthora palmivola, a phytopathogenic microorganism effective against strangle vein (Morrenia odorate), an Asclepiadaceae weed, Collego (a product of Ecogen) using spores of Colletotrichum gloeosporioides, a phytopathogenic microorganism effective against northern jointvetch (Aeschynomene viginica), a leguminous weed, and others are commercially available.
Other ongoing research with phytopathogenic microorganisms includes those of genus Hypomycetes having pathogenicity to kuroguwai (Eleocharis kuroguwaiohwi), a rice paddy weed, and Cercospora rodmanii having pathogenicity against water hyacinth (Eichhornia crassipes), an aquatic plant.
Meanwhile, the development of herbicides containing phytopathogenic microorganisms against barnyard weeds is progressing in Japan, and such herbicides and methods of application have been proposed (Japanese Patent Laid-open (Kokai) No. 1994/321721; Japanese Patent Laid-open (Kokai) No.1996/40816). Japanese Patent Laid-open (Kokai) No. 1994/321721 discloses a technique in which a new microorganism belonging to genus Curvularia was suspended in an organic solvent supplemented with a surfactant to better preserve said microorganisms and to improve their dispersion in water.
In such herbicides containing phytopathogenic microorganisms, it is advantageous to use a conidium of a phytopathogenic microorganism because of its durability. However, a conidium having a hydrophobic surface has been difficult to produce and use as a herbicide because of its inherent low affinity to water.
For example, conidia of Drechslera monoceras, which is pathogenic against barnyard grass, a weed in rice paddies, have a higher specific gravity than water, but when directly seeded on rice paddies, the conidia float on the surface of the rice paddies. If the conidia float on the water surface and cannot submerse, the conidium has a decreased chance to make contact with the barnyard grass. Thus, the use of this microorganism cannot have a sufficient herbicidal effect against barnyard grass. Conidia float on the surface of rice paddies because the surface of the conidia is inherently hydrophobic such that they repel water due to the surface tension of water. Conventionally, in order to solve this problem, a surfactant or the like is added to a conidium fraction so as to increase the affinity of the conidia to water (Japanese Patent Laid-open No. 1994/321721).
The hydrophobic surface of a conidium of phytopathogenic microorganisms also has an adverse effect on the production of a conidium fraction, specifically, the aggregation of the conidia causes difficulty in handling and lowers recovery. A surfactant has conventionally been used to resolve this problem.
Thus in the production of phytopathogenic microorganisms having a hydrophobic surface, and the formulation of a herbicide containing said microorganisms as an effective component, said microorganisms have always had a sufficient amount of adhered surfactant.